1. Field of the Invention
This invention involves a security patrol system.
2. Prior Art
There are a variety of known means to acknowledge the presence at predetermined locations of a guard who is assigned the task of investigating those locations. Typically, the locations are scattered throughout a building so that the guard must walk through essentially all of the building to reach all of the predetermined locations. The most prevalent system, probably for economic reasons, involves a guard carrying a time clock which he punches with differently coded keys channeled to different monitoring stations. Such a system is cumbersome, but has been the industry standard for years.
In some applications, this archaic system is totally unacceptable. For example, in prisons or jails, it is dangerous for a guard to carry a heavy time clock since he may be attacked by a prisoner and bludgeoned with his own clock.
To overcome such objections and to streamline guard monitoring systems, prior artisans have suggested remote units placed at the monitoring locations and connected to a central monitoring control system. The prior art teaches various specific apparatus having such remote guard stations and central control systems, but none have achieved any apparent commercial success.
U.S. Pat. No. 3,237,183 issued to R. F. Eagan on Feb. 22, 1966 teaches a monitoring system in which the guard energizes relays associated with each station as he proceeds with the tour. When the tour has been completed, all of the relays will be latched in the energized position. The system is then reset by pressing a switch which cuts off power and the relays become de-energized. U.S. Pat. No. 2,559,746 issued to L. F. B. Ahlberg et al. on July 10, 1951 discloses a control station with circuitry connected to relays associated with guard stations and to a recording device. The recording device includes an electromagnet with an associated writing pen in a recording instrument. When a relay is released by the watchman breaking the contact at the control station, the recording device is activated.
The Eagan and Ahlberg et al. patents both have an involved central control system connected with each of the remote stations. Each of the guard stations requires an associated plurality of relays and current paths to determine the presence of a guard at any of the stations. Each additional component adds to the complexity and cost of fabrication, reduces reliability, and adds to the space required for installation of the system.
U.S. Pat. No. 2,298,840 issued to G. G. N. Purcell on Oct. 13, 1942 discloses an alarm system in which a portable transmitter carried by a watchman is inserted into a transmitting station to transmit signals characteristic of each station to connected control equipment. U.S. Pat. No. 1,394,838 issued to C. C. Johnson et al. discloses a portable register which is actuated each time a watchman reaches a station. When the watchman reaches the end of a tour, he may connect suitable transmitting mechanism within his register to a suitable circuit and may then send a signal indicating he has completed the tour.
The Purcell and Johnson et al. patents add the additional complexity of a portable device to be carried by the guard and used at each guard station. An interaction between the central control system associated with each guard station and the portable device provides the indication of the guard at the particular station. The addition of the portable device adds to the cost of the system and adds components which may fail to perform properly. Also, there still remains a plurality of relays and current paths associated with each guard station.
Thus, attempts to modernize guard monitoring systems have resulted in complicated and expensive electronic nightmares. They have achieved no apparent successes.